To Roundup or Not To Roundup—That is the Question
No doubt about it, the world of food plots has evolved tremendously. Gone are the days of people asking what a food plot is. Also gone is the question of whether food plots are a viable tool in habitat management and improvement. Over the past few years I have witnessed “food plotters” graduate to a new level of education and are now asking questions that are much more advanced than in the past.
One glaring example of this is the sudden interest in the use of herbicides in the planting and maintenance of food plots. The Whitetail Institute, in keeping with its leadership role in the industry, introduced the first ever line of herbicides designed for food plots. Two years ago Arrest (grass control) and Slay (broadleaf weed control) burst onto the market with incredible fan-fare. Even with the tremendous success of these two products, there is little debate on which herbicide is the most asked-about product.
Roundup, a Monsanto product, is a broad spectrum herbicide that for years has been well known to farmers, gardeners, homeowners and literally anyone with a green thumb. Roundup can be found at nearly every store that has anything to do with growing plants and is arguably the most widely used herbicide on the market. Of course, deer hunters and managers are also interested in how Roundup can be used in their food plot practices. In fact, I have fielded innumerable questions about Roundup and its application in a food plot program. With this being said, there are quite a few misconceptions and misunderstandings of how Roundup works and how it can be effectively used. In this article we will examine the what, how and when of Roundup usage and hopefully answer some questions you may have.
Active Ingredient and Mode of Action
To begin, it would be prudent to discuss what exactly Roundup is and the mode of action it uses to kill plants. The active ingredient found in Roundup is called glyphosphate. Glyphosphate kills plants by inhibiting a specific enzyme that is needed by plants for growth. This enzyme is called EPSP synthase. EPSP synthase is essential in the production of proteins needed for normal plant growth. When this enzyme is inhibited by glyphosphate, these growth proteins are not produced and the plant will begin to yellow and slowly die over a period of days. Glyphosphate is effective on nearly all green vegetation as this same enzyme is used by most plants.
Application
Glyphosphate is considered a post-emergent herbicide. What this means is that it has no residual in the soil and is only effective on growing plants. Once glyphosphate enters the soil, it basically denatures and will not have any effect on seeds in the soil. Do not be surprised that a few weeks after a Roundup application, new weeds will start to emerge. This is especially true if you have tilled or worked the soil after the Roundup was applied.
The leaf of a plant is the principle means by which Roundup is absorbed, therefore, adequate glyphosphate to leaf contact is important. One thing that can aid in this is using a surfactant with the glyphosphate/water spray mix. A surfactant is a chemical that helps a herbicide “stick” to the plant leaf. This is why you may have heard surfactants called “stickers”. In actuality, surfactants don’t exactly make the herbicide sticky, at least in the way you might think. Surfactants instead help to bead the herbicide and make it more likely to stay on the leaf when sprayed. This is especially true when spraying broadleaf weeds.
Yet another chemical that is sometimes added to a Roundup herbicide mix is crop oil. The main function of crop oil is to increase the rate of absorption of the herbicide through the leaf. Crop oil is often used when spraying hard-to-kill grasses such as fescue or Johnson Grass.
When to Use Roundup for Food Plot Applications
Roundup can be a very effective tool when putting in food plots, but understanding Roundup characteristics and relating them to the appropriate application will give you better results.
The most common use of Roundup in the food plot world is when a new area is being planted or an existing field that has been overtaken with weeds is being replanted. When planting a food plot in an area that has not been planted before or at least not recently planted, it will more than likely be over-grown with weeds and/or have a heavy sod base requiring you to “break” the ground. Proper ground-breaking is instrumental in the creation of a good seed bed but is often times the hardest step for many food plot practitioners. This is especially true for those who do not have access to heavy tillage equipment or are planting in an area inaccessible to heavy tillage equipment.
The root structure of the existing vegetation creates a hard and tight top layer of soil much like re-rod does with cement. If you are using light equipment such as a 4-wheeler implement, the initial breaking of the ground can be an arduous task. You simply may not have enough weight and power to break through the sod base. Breaking a heavy sod-based ground with this type of equipment will take some time and will more than likely not kill the entire root structure of the plants. In these cases, spraying Roundup before you try to break the ground can make your lighter tillage equipment much more effective. The reason is that glyphosphate will kill the entire plant, including the roots, essentially removing the “re-rod” from the soil.
If you find yourself faced with this scenario, first examine the existing vegetation. If you have mature and/or tall plants you may want to mow the area first. This will help you in two ways. First it helps to break down the heavy ground cover and second, it will cause the mature plants to begin fresh new growth, making your herbicide application more effective. If you do mow, you will need to wait at least a week before spraying for the new weed growth to start. All herbicides are more effective when plants are actively growing.
The next thing you need to consider is that most gylphosphate herbicides require 10 to 14 days to completely kill the plants so you will need to allow yourself two weeks between spraying and breaking the ground. If you have heavy equipment such as turning plow or PTO driven tiller, you will likely not need to use Roundup before you break the ground as the equipment you are using will cut thru the roots, killing the vegetation.
One of the most important things to remember when using Roundup for creating food plots is that glyphosphate will not kill the seeds in the soil. As we mentioned earlier, Roundup is a post-emergent herbicide and is only effective on growing plants. I have had many a food plotter ask me why even after they sprayed Roundup and tilled the plot, a few weeks later they still had weeds coming up in the plot. The answer is that there can be literally millions of plant seeds in the ground. They can sit there dormant for a long time waiting for the right conditions for germination. If you have sprayed and tilled the ground, killing all existing weeds, you have also brought new weed seed to the surface, giving the right conditions for germination. You find yourself in somewhat of a catch-22. You need to spray and till to get rid of the weeds and create a seed bed, but in the process you make it possible for new weeds to grow.
To try and help with this predicament, a method was developed that is probably the best way to get as close to a weed-free seed bed as possible. The following is a step-by-step procedure for this method.
i. Disk the ground several times.
ii. Run a drag over the ground to level the seed bed.
iii. Go over the seed bed with a cultipacker to further level and firm the seed bed.
Without question this method requires planning and time. The process can take up to four to six weeks to complete. But with a little patience and planning, you can produce as close to a weed-free food plot as you can get. This method is especially effective on trouble fields or ones that have a history of being very weedy.
Spraying Roundup on Existing Food Plots
In the past couple of years, there has been much talk about using a very low-concentrate, “watered-down” Roundup application on perennials such as Imperial Whitetail Clover to kill the weeds but not kill the clover. Admittedly, I have seen this work and have even experimented with it myself with success. Because of Imperial Clover’s extraordinary hardiness, a watered-down glyphosphate mixture will often times kill less hardy weeds and not significantly harm the clover. However, I have also seen some catastrophes.
The basic problem is that Roundup will kill Imperial Whitetail Clover. There is no exact science to “watered-down” Roundup method and furthermore there are several other variables that can create problems. Some of these variables include sprayer calibration, ground speed, wind, rainfall, plant maturity, improper mixing and host of others. A problem with any one of these variables can cause your beautifully green Imperial Clover field to turn brown and die. In my opinion, a far better option is to use herbicides that are designed to kill weeds and grasses but not harm the clover, such as the recently-introduced Arrest and Slay herbicides.
Without question, Roundup can be used as an extremely effective tool in planting food plots. Realizing how it works, when to use it and how to use it will help you to maximize your efforts.
THE WHITETAIL INSTITUTE DOES NOT RECOMMEND ROUNDUP BE USED ON ANY IMPERIAL WHITETAIL PRODUCT FOR WEED OR GRASS CONTROL.